1. Field of the Invention
The present invention relates to a feedback controlled tension applying system for supplying a material in continuous sheet form to a material processing device while applying a tension, which is controlled to be an appropriate value, to the material.
2. Description of the Related Art
The conventional feedback controlled tension applying system of this type is disclosed in Japanese Patent Laid-open No. 2002-102938. This feedback tension applying system is applied to a corrugated fin processing device for manufacturing corrugated fins for automotive heat exchangers and includes a slit processing device that separates a continuously supplied fin material in sheet form into two rows, a corrugation processing device that processes the fin material separated into two rows in a longitudinal direction into corrugated form, a tension applying device that is arranged in the upstream side or down stream side of the slit processing device and applies a tension to the fin material, and a load cell that measures the tension by measuring a reaction force that acts on tension measuring rolls, which press the fin material placed between two support rolls, in order to control the tension applying device.
The tension applying device is then feedback-controlled so that a load value measured by the load cell becomes a set value that is set in advance. While applying a predetermined tension to the fin material, the fin material is controlled so that a supplying length of the fin material to the slit processing device and to the corrugated fin processing device becomes a predetermined length.
However, in the above-described conventional feedback controlled tension applying system, the value of appropriate tension to be applied to the material changes in each case according to processing accuracy of the corrugated fin processing device and the type or kind of fin material, so that, when attempting to control the supplying length of the fin material to the corrugated fin processing device to be a predetermined length, a load of the load cell corresponding to the predetermined length is needed to be changed in each case. Therefore, there has been a problem that considerable time and work are needed to set or adjust the set value of the tension that is set in advance.
Further, the tension of the fin material that is applied by the tension applying device is a substitute value for a supplying length amount per predetermined time, for example per unit time, of the fin material to be supplied to the corrugated fin processing device (corresponding to supplying speed of the fin material), and when the tension applying device is feedback-controlled based on a measurement result, not a moving length amount per predetermined time but a load, of the load cell, there has been a problem in that, if dispersion in height, length, louver angle or the like of a processed corrugated fin occurs, it is difficult to identify a cause of the dispersion.
Furthermore, since the tension applying device uses frictional forces of felt pads that sandwich the fin material as a method for applying a tension to the fin material, there has been a possibility of product variation caused by a change of coefficient of dynamic friction of the fin material, a rapid increase of load to the fin material when the corrugated fin processing device transit from a halt state to an operating state, or the like.
The present invention is made in view of the above described problems, and an object thereof is to provide a feedback controlled tension applying system that is capable of easily changing a setting of control to make the length per unit time of the material supplied to the material processing device become a predetermined value when the processing accuracy of the material processing device or the type or kind of a fin material are changed when supplying a material in continuous sheet form to the material processing device while applying a tension to the material, and is capable of improving the precision of products processed by the material processing device.